Feeding amounts on pet food bags are broad guidelines for average animals — your pet is not average. A weight- and activity-based estimate is a far better starting point than a bag chart.
From energy needs to grams
Pets need calories first. Resting needs scale sub-linearly with weight (70 × kg^0.75), and activity multiplies that up. Only then do you convert calories to grams — the conversion depends entirely on how energy-dense the food is.
Why the label matters
Two foods can look identical per serving yet differ by 30% in calories. Energy density (kcal per 100 g) is the missing number that turns a calorie target into an accurate portion.
Adjust by body condition, not the number
The calculated portion is a start. The pet's body condition — ribs feelable but not visible, visible waist — is the real feedback. Weigh weekly and move the portion in small steps.
Frequently asked questions
It depends on weight and activity. A 20 kg moderately active dog needs about 800 kcal/day — around 230 g of a typical 350 kcal/100g dry food.
A 4 kg moderately active cat needs roughly 270 kcal/day — about 77 g of dry food, usually split into two meals.
No. It's a starting point. Puppies, kittens, nursing mothers and pets with conditions need veterinary guidance on portions.